Abstract

Loss compensation in long-range dielectric-loaded surface plasmon-polariton waveguides is theoretically analyzed when rare-earth-doped double tungstate crystalline material is used as the gain medium in three different waveguide configurations. We study the effect of waveguide geometry on loss compensation at the telecom wavelength of 1.55 μm, and demonstrate that a material gain as small as 12.5 dB/cm is sufficient for lossless propagation of plasmonic modes with sub-micron lateral confinement when using waveguide ridges with gain.

Figures (8)

Layout of the LR-DLSPP structures with gain analyzed in this work: (a) Gain material, RE-doped double tungstate, as buffer layer and ridge in BCB; (b) gain material in the buffer and polyimide ridge; (c) gain material in the ridge, buffer layer in silicon nitride and 100-nm-thin BCB adhesive layer between buffer and ridge. The wavelength utilized in all the simulations is 1.55 μm.

(a) Mode profile for Structure 1 with hbuffer = 60 nm and hridge = wridge = 1.4 μm; (b) vertical line scan of the mode profile across the center of the metal stripe (x ~0). It can be seen that the electric field hardly penetrates inside the gain buffer material.

Structure 3: Net optical loss as a function of hbuffer for (a) hridge = 0.8 μm and various wridge and (b) wridge = 0.8 μm and various hridge; confinement of the optical power to the active material region (ridge) as a function of hbuffer for (c) hridge = 0.8 μm and several wridge and (d) wridge = 0.8 μm and several hridge; mode width in the x-direction as a function of hbuffer for (e) hridge = 0.8 μm and various wridge and (f) wridge = 0.8 μm and various hridge. The material gain was considered to be zero in all cases (passive structure).